This invention relates to a panel heat exchanger having a plate made of a heat-conducting material and at least one pipe connected with it, particularly in a meandering shape, through which a heat exchange medium can flow.
Panel heat exchangers of this type are shown in German Utility Model 8,304,603. In the exchanger of that reference, coiled pipes are provided that are bent in a meandering shape. These pipes are fastened at carrier sheets consisting preferably of aluminum or aluminium forging alloys by clamps that are punched out of the plane of the carrier sheets and are placed around the pipes. The pipes that are fixed at the plate advantageously have a triangular cross-section for better fastening, and may subsequently be covered by a second plate. Exchangers of this construction have a disadvantage in that when this type of panel heat exchanger is installed, the lugs and holding clamps may represent a danger that could result in injury. For this reason, the second covering plate must be provided, and the heat transfer between the pipe and the plate is not sufficient because of the relatively small contact surfaces between the clamps and the pipe.
A panel heat exchanger in which the coiled pipe is glued to the carrier sheet is shown in German Published Application 3,308,329. That panel heat exchanger has a disadvantage in that there is a poor heat transfer between the coiled pipe and the plate because the glue has low thermal conductivity. It also has the disadvantage that, in manufacturing, the coiled pipe and the carrier plate must remain braced with respect to one another during the hardening process of the glue. This process is expensive and, because of the hardening time, makes series production less attractive. In addition, such a glued connnection is not sufficiently reliable for highly stressed products, such as, for example, are used in motor vehicles.
The present invention has an objective of providing a panel heat exchanger of the initially-described type that is simple to manufacture but nevertheless ensures a good heat transfer between the pipe and the carrier plate.
This and other objects of the present invention are attained in a panel heat exchanger provided with slots for receiving a pipe so that the pipe is inserted into the slots approximately flush with the plate. The pipe has deformations extending transversely to its longitudinal axis, and is thereby held at the slot edges.
The deformations held at opposite exterior sides of the pipe, create continuous contact surfaces between the pipe and the carrier plate that ensure a good heat transfer, as is the case between the ribs connected to a pipe. The manufacturing of the new panel heat exchanger, according to the invention, however, requires neither gluing nor soldering and can be carried out in a simple way.
The heat transfer between the pipe and the plate may also be improved in certain preferred embodiment by selecting the width of the slots to be slightly smaller than the pipe diameter. As a result, there occurs during the positioning of the pipes in the slots of the plate, a certain deforming of the slot edges that place themselves continuously against the shell of the pipe. If the deformations are provided with creases that overlap the opposite slot edges, a stable closure is created in addition to the frictional connection between the pipe and the slots. The panel heat exchanger is thus extremely sturdy and has excellent heat transfer characteristics.
It is advantageous, in certain preferred embodiments, not to let the slots for the insertion of the pipe or the coiled pipe extend to the edge of the plate. In these embodiments, at least the two connecting ends of the pipe are led out of the plane of the plate bent at approximately right angles. The plate itself may therefore be very sturdy because the slots for the inserting of the pipe or pipe coil are located only within the plate surface so that the plate retains a stiff surrounding edge.
In preferred embodiments in which the pipe has a serpentine shape with straight legs that extend in parallel to one another, it is advantageously provided in certain of these embodiments, to hold only these straight legs in parallel slots within the plate. The connecting arches of these straight legs project at a right angle out of the plane of the plate and only rest on the plate. It was found that the resulting loss of heat-transferring contact surfaces in these embodiments is not so large so as to outweigh the resulting simplification of manufacture. Mainly, it is very simple for this embodiment to provide the creases on both sides of the plate so that the pipe in the area of its parallel legs rests not only against the front sides of the slot edges but via the creases also against the edge areas of the plate that are adjacent to the slot. As a result, the heat transfer area is clearly enlarged.
In another preferred embodiment, the slots are interrupted by transverse webs which are deformed to be semicircular either before or during insertion of the pipes. In this case, the pipe will be provided with creases only on the side of the plate that is opposite the transverse webs. It is also contemplated to provide such a construction in the area of the connecting arches of the serpentine-shaped bent pipe so that it is not necessary to lead the connecting arches out of the plane of the plate bent at a right angle. Nevertheless, in the area of the connecting arches, a crease arrangement that extends at both sides does not need to be provided, the manufacturing of which is possible but in view of a later bending of the plate for the adaption to installation conditions, is not advantageous.
In a further preferred embodiment, the deformations are arranged only at separate points at distances behind one another along the pipe, in which case adjacent deformations are also arranged alternating on one or the other side of the pipe projecting out of the plane. This has the advantage that the fastening of the pipe in this manner in the slot can take place largely without concern for tolerances, namely in the area of the connecting arches of serpentine-shaped bent pipes. In this type of deforming of a pipe in serpentine shape, it is contemplated that the slot therefore also have a shape that is adapted to this serpentine shape.
For the manufacturing of the preferred embodiment of a panel heat exchanger according to the present invention, a device with a holder for holding the plate, and a die movable with respect to the holder was found to be particularly advantageous. By means of this device, the coiled pipe can first be positioned in the carrier plate and can subsequently be fastened in a form-fitting way.
Further objects, features, and advantages of the present invention will become more apparent from the following description when taken with the accompanying drawings, which show for purposes of illustration only, preferred embodiments constructed in accordance with the present invention.